Association leaders who met in Ankeny this week reaffirmed their support for the plan, which was released last month. ISA President Mark Jackson says the plan is based on science, recognizes the diversity of the state's landscape and is "much more effective than a costly, one-size-fits-all effort to improve water quality."

The plan calls on wastewater treatment plants to make upgrades to reduce their discharges into waterways. But it asks farmers to take voluntary steps to reduce the runoff caused by fertilizers and manure on farm fields.

Critics say they doubt a voluntary approach will have much impact.

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